Antigen-specific immunity is mediated by humoral antibody and receptor-bearing T lymphocytes. Although antibody molecules have been characterized in detail, the antigen-specific receptor on T lymphocytes has only recently been identified by monoclonal antibodies, and the primary structure is still not known. This proposal takes advantage of a recently isolated cDNA clone that appears to encode one chain of the T cell antigen receptor. The first set of experiments are aimed at determining the primary structure of the receptor by nucleic acid sequencing. Receptor genes will be cloned and sequenced from T cell hybridomas specific for species variants of cytochrome c. The goal will be to characterize the delineation of variable, joining, and constant regions, the presence (or absence) of framework and hypervariable regions, and the amino acid residues important in determining antigen specificity, Ia specificity or both. The second set of experiments focuses on the expression patterns of this and other cross-hybridizing receptor genes in different T cell subsets. Cytotoxic and suppressor cells will be examined for genomic rearrangements (on genomic Southern blots), and mRNA expression (on Northern blots), and the expressed genes from these cells will be cloned and sequenced. Analysis of the data will focus on comparisons between sequences of functionally different T cells. The third set of experiments will focus on cell surface receptor expression relying on antibodies made to synthetic peptide homologues. Experiments will be designed to determine the levels of receptor expression by different cell types and at different stages in T cell differentiation. A long term goal of studying the structure of the T cell receptor will be to determine structure-function relationships by directed mutagenesis and DNA-mediated gene transfer. The proposed experiments lay the groundwork for such future endeavors.